Treatment of sour hydrocarbon distillate



Jah. 12, 1960 P, URBAN ETAL TREATMENT OF' SOUR HYDROCARBON DISTILLATEFiled Dec. 18. 1957 @a02 uso," l

s u l /V VEN TORS: Peter Urban Wfl/iam K. T. Gle/m 5K y MM A Tron/v5 YS.

mmub Som.

UnitedStates Patent* F SOUR HYDROCARBON DISTILLATE l i Peter Urban,Northbrook, and William K. T. Gleim, ls-

land Lake, lll., assignors, by mesne assignments, to Universal OilProducts Company, Des Plaines, Il l., a corporation of DelawareApplication December 18, 1957, Serial No.l 703,544 14 Claims. (Cl.208-205) TREATMENT captans by contacting the hydrocarbon distillate withan alkaline solution. Mercaptides formed during this contacting aresoluble in the alkaline solution, and the alkaline solution'is separatedfrom the treatedrdistillate and subjected to regeneration. Although manyattempts have been made in the past to regenerate the alkaline solutionby oxidizing the mercaptides to disulfides, this process has notattained 'commercial success because eicient and sufficient regenerationhas not been obtained. Various modifications have been attempted butstill have been unsuccessful. For example, a proposed solutionof thisproblem has been the use of a metal chelate such as disalicylal ethylenediamino cobalt. However, this and previously suggested compoundsdecompose during use, with the unsatisfactory result that the catalystis of very short life and, probably more important, the cobalt or othermetal is entrained or dissolved in the treated hydrocarbon distillate.The metal in the distillate acts as a pro-oxidant to catalyzeundesirable oxidation reactions, with the resultant formation of gums,discoloration, and other deleterious effects. i

Recently it has been found that certain phthalocyanine'compounds areextremely effective catalysts for oxidizing mercaptans or mercaptidesand that these phthalocyanine compounds are stable during use. With thisnew discovery, a lnovel process has been developed for effectingsweetening of hydrocarbon distillates, `with regeneration of thealkaline solution now being efficiently accomplished by oxidation.During oxidation of the alkaline solution, disulfides are formed,thedisuldes beingdispersed through the alkaline solution. In accordancewith the present inventionthe disuliides varecoalesced and settled, thedisuldes beingseparately withvdrawn from the regenerated alkalinesolution and the latter is reused in the process. T hisI isan importantstep in the presentV process because a major portion ofthe sulfurcompounds thus are removed and are not returned tothe gasoline with theregenerated alkaline solution. Sulfur compoundsV appear to reduce thetetraethyl lead Susceptibility of gasoline and, therefore, inyaccordance with the present invention a substantial proportion-of thesulfur compounds are removed separately from the process. y n l Inaccordance with the present invention the hydrocarbon distillate is rstextracted with an alkaline solution v to remove a major portion of themercaptans, the alkaline solution then is regenerated by oxidation inthe presence tion containing entrained or sorbed oxygen and/ or oxygenVICC compounds is :contacted with the partly treated hydrocarbondistillate n order to oxidize mercaptans remain-v ing in the gasoline.This produces a sweet or substantially sweet gasoline product. Animportant advantage to this novel method of final treating is that theoxygen and/ or oxygen compounds contained in the alkaline solu-V tionare suiicient to oxidize remaining mercaptans but' are not in excesswhich may have a deleterious effect on the hydrocarbon distillate.

From the above description it will be seen that a sweet or substantiallysweet product is obtained by the novel process of the present invention.While removal of a major proportion of the mercaptans normally isreadily obtained, removal of the remaining small amount of mercaptans isditlicult and requires complicated and expensive treatments, such ascopper treating, sodium plumbite treating, etc. These costly treatingsteps are avoided by the novel process of the present invention in whichnal sweetening is accomplished by a novel oxidizing treatment. Ashereinbefore set forth, it is only because of the recent availability ofthe phthalocyanine catalyst that the improvedV process is attained.

The phthalocyanine catalyst is both very active and highly stable.Because of its high activity, the catalyst is used in exceedingly smallconcentrations. These may range from 5 to 500 and preferably l0 to 100parts per million by weight of the alkaline solution, although lower orhigher concentrations may be used in some cases. The use of higherconcentrations are unnecessary in most cases but may be used if desired,and thus may range up to 25% or more by weight of the alkaline solution.Because of its high stability, the catalyst is used for exceedingly'long periods of time. As will be shown in the following examples,caustic solution containing 50 parts per million of cobaltphthalocyanine disulfonate has been used toV treat an equivalent of36,000 barrels of gasoline, and the catalyst stillwas very active andcan be used to treat additional gasoline.

The present invention is especially suitable forthe sweetening ofhydrocarbon distillates and particularly sour gasoline, includingcracked gasoline, straight'run gasoline or mixtures thereof, naphtha,jet fuel, kerosene, aromatic solvent, stove oil, range oil, fuel oil,etc. Other hydrocarbon distillatesinclude lube oil, as well as normallygaseous fractions. In still another embodiment the novel features of thepresent invention may be utilized for purifying other organic fractionscontaining certainy acidic impurities..k These organic compoundsincludelalcohols,'ketones, aldehydes, etc.

Anysuitable alkaline solution is utilized in the proc? ess and comprisesparticularly sodium hydroxide (caustic), potassium hydroxide,A etc. Thealkaline solution gen.-V erally isfutilized as-'an aqueous solution offro'm-about -5 to about 50% weightv concentration. Whenrdesired;

solutizers, solubilizing agents, ete.`are employed includl ing, forexample, alcohols and particularly methanol, ethanol, etc., phenols,cresols, butyric acid, etc., in order to increase the contact and/orreactionof the acidic com` pounds with the alkaline reagent.'Arparticularly pre` ferred agent for this purpose is methanol and itsuse will be described hereinafter in further detail. In some cases vthe,4hydrocarbon distillate contains' phenol compounds in suicientconcentration to serve'this purpose; otherwise they may be introducedfrom an-extraneous source. Vg f g AnyY suitable phthalocyanine catalystmeeting ,thepre` quirements of high activity and stability during usemay: be employedl in the present invention.- AParticularly pref ferredmetal phthalocyanines comprise, cobalt phthal` ocyanine and `vanadillmphthalocyanine The -metal phthalocyanine in general is not readilysoluble inaque-44 @Us ,Solutions and, thetefqrafor, improvedcperatienlspreferably utilized as a derivative thereof. A particularly preferredderivative is the sulfonated derivative. Thus, a preferredphthalocyanine catalyst comprises cobalt phthalocyanine disulfonate.Another preferred catalyst comprises vanadium phthalocyaninedisulfonate. These compounds may be obtained in the open market or maybe prepared in any suitable manner as, for example, by reacting cobaltor vanadium phthalocyanine with 20% fuming sulfuric acid. While thesulfonic acid derivatives are preferred, it is understood that othersuitable derivatives may be employed. Other derivatives includeparticularly the carboxylated derivative which may be preperad, forexample, by the action of trichloroacetic acid on the metalphthalocyanine or by the action of phosgene and aluminum chloride. Inthe latter reaction the acid chloride is formed and may be converted tothe desired. carboxylated derivative by conventional hydrolysis.

The invention is further explained with reference to the accompanyingflow diagrammatic drawing which illustrates several specific embodimentsof the invention. It is understood that the broad scope of the presentinvention is not limited to the specific illustrations in the drawing.

In the interest of simplicity the drawing will be described withreference to the sweetening of a sour gasoline. with caustic solution(sodium hydroxide) containing cobalt phthalocyanine disulfonate,although it is understood that other organic compounds, other alkalinesolutions and other phthalocyanine compounds may be used as hereinbeforeset forth. Referring to the drawing, sour gasoline is introduced intothe process through line 1 and is directed, preferably through asuitable distributing device indicated at 2, into extractor 3. When thesour gasoline contains hydrogen sulfide, it may be given a prior washwith an alkaline solution and preferably caustic solution to removehydrogen sulde by conventional means, not illustrated. In the case hereillustrated, zone 3 comprises'a vertical extraction zone, whichpreferably contains suitable packing material and/or contacting means,including bafes, side to side pans, bubble trays, bubble decks, etc. Apacking material preferably also is utilized and should be one that willnot be detrimentally affected by the alkaline solution and hydrocarbonsat the operating condition prevailing in thiszone. A particularlysuitable packing material comprises carbon Raschig rings. It isunderstood that two or more extraction zones may be employed and alsothat horizontal extraction zones may be4 employed.

In zone 3, the gasoline ows upwardly in intimate contact with causticsolution containing cobalt phthalocyanine disulfonate, introduced in themanner. to be hereinafter set forth to zone 3 through line 4, preferablythrough a suitable spray arrangement illustrated at 5. When desired,fresh caustic may be introduced, or spent caustic withdrawn, by way ofthe extension of line 4. During contact of the gasoline with the causticsolution, acidic organic compounds, such as mercaptans and phenolscontained in the gasoline, are converted into sodium mercaptides andphenolates and are dissolved in the alkaline solution. The rates of liowof the gasoline and alkaline solution areV adjusted so that the treatedgasoline being withdrawny from zone 3 through line 6 containssubstantially less mercaptans than the sour gasoline introduced; throughline 1.

Treatment of the gasoline with caustic solution in zone 3 may beeffected at any suitable temperature, which temperature is above thefreezing point of the caustic solution. Generally ambient temperature issatisfactory, although in some cases lower or higher temperatures may beused, ranging from as low as about 25 up to about 220 F. Preferablytemperatures of from about 80 to about 110'F. are employed; Any suitablepressure may be employed and generally is within the range ofy fromabout 25` to 200 pounds per square inch, although lower orhigher-pressuresmay be employedin some cases: Preferablysuperatmospheric pressure is employed in the system in order tofacilitate recovery of hydrocarbons from the excess air subsequent tothe regeneration of the caustic solution when desired.

The spent caustic solution containing cobalt phthalocyanine disulfonateand sulfur compounds is Withdrawn from the lower portion of zone 3 andis directed by way of line 7, preferably through a suitable sprayarrangement illustrated at 8, into regenerator '9'.V Air, oxygen orother suitable oxygen-containing gas is introduced into zone 9 throughline 10 and preferably through a suitable spray arrangement asillustrated at 1'1. In regenerator 9 sodium mercaptides are oxidized toregenerate sodium hydroxide and to oxidize the sulfur components todisulfides. Oxidation in zone 9 may be effected at any suitabletemperature, which generally will be within the ranges hereinbefore setforth in connection with the description of zone 3; Excess air iswithdrawn from the system through line 12 and may be reused in theprocess or disposed of as desired.

The regenerated caustic solution, cobalt phthalocyanine disulfonic anddisuldes formed in zone 9 are withdrawn as a mixture through line 13 andare passed into coalescer 14, preferably through a suitable sprayarrangement as illustrated at 15. As hereinbefore set forth, oxidationof the caustic solution in zone 9 results in a formation of disulfides.In order to avoid the deleterious effects of disulfides in the gasoline,it is important that the caustic solution be treated to remove thedisulfides prior to recycling of the caustic solution for further use inthe process. The disuldes contained in the caustic solution beingwithdrawn through line 13 are in finely dispersed condition and are notreadily removable. This is accomplished in the present process bysubjecting the mixture to treatment in zone 14 to coalesce theydisulides so that they may be separated from the caustic solution. Anysuitable coalescing system may be employed and preferably comprisespassing the causticdisulfide mixture through a bed of sand, straw, glasswool, etc. A. particularly effective coalescing agent is prepared bycoating sand with a material available on the market as Desicote whichis an organo silicone chloride. The mixture then is withdrawn from zone'14 throughline 16 and is passed into settling zone 17.

In zone 17 an upper disulfide layer separates from an aqueous causticsolution layer containing cobalt phthalocyanine disulfonate. Thedisulfides are withdrawn through line 18 and may be used for any desiredpurpose. The regenerated caustic solution now substantially free from.disulfides but containing cobalt phthalocyanine disulfonate is withdrawnfrom settler 17 through line 19 andl amajor portion thereof is recycled,in one embodiment of the invention, by Way of lines 19 and 4 toextractor 3 for further use therein.

The regenerated caustic solution being recycled by way of line 19 inmany cases will ycontain entrained or sorbed oxygen and/or oxygencompounds which, when the caustic solution is returned to `extractor 3,will cause oxidation of mercaptans therein to disultides. The disulfideswill remain in the gasoline, and this increases the total sulfur contentof the gasoline which, in many cases, is undesirable. In order to reducethe oxygen content of the recycled caustic solution, one and preferablyboth of the following methods are used. In one method, a portion (aboutl to about 25 volume percent) of the rich caustic solution Withdrawnfrom extractor 3 through line 7 is passed through line 20 to comminglewith the regenerated caustic solution in line 19. The oxygen containedin the regenerated caustic solution is consumed by oxidizing mercaptansand/01 sodium mercaptides contained in the rich caustic solution. Hereagain, it will be noted that'the caustic solution contains the cobaltphthalocyanine disulfonate catalyst. and this catalyst serves to effectsuch oxidation. In the second method, the regenerated caustic solutionbeing passed through line 19,

aaamaa either with or without `the-.rich caustic solution being passedthrough line 20, is directed through line 21, heated in exchanger 22 andthen directed through line 23 `and line 24 into line 19 for return toextractor 3. Heating of the caustic solution causes turtherpoxidation ofthe more diffcultly reacted mercaptans contained in the rich causticsolution, and this in turn consumes oxygen contained in the regeneratedcaustic solution. The caustic solution preferably is heated to atemperature within the range of from about 100 to about-300 F. and moreparticularly of from about 140 to about 200 F.

While the heated and reacted caustic solution may be returned by wayof'lines 23, 19 and.4 Ito extractorS, preferably the disullides formedby the additional reaction are removed from the caustic solution priorto reuse `of the latter in the extraction zone. In one embodiment thisis accomplished by directing the heated and reacted caustic solutionthrough line 25 into Ydisulfide removal Vzone 26, preferably through asuitable spray arrangement illustrated 'at 27. One method. of removingthe disulfdes is by extracting the disuldes from the caustic solutionwith a hydrocarbon distillate. While any suitable hydrocarbon distillatemay be used, in a preferred embodiment it comprises allow boilinghydrocarbon fractionfsuchaspentane,hexane or vmixtures thereof, whichare intro- `duced to zone 26 through line 28, preferably through asuitable spray arrangement illustrated at 29.. The hydrocarbondistillate is withdrawn from zone 26 through line 30 and, when a lowboiling distillate is used, the distillate may be separated from thedisuldes by distillation and the recovered distillate'then maybe reusedin the process, The regenerated caustic solution now free 'of disultidesis withdrawn from zone 26 through line 31 'and is passed by wa'y oflines 19-'and 4to extractor 3 for further u setherein. In anotherembodimentof the invention, removal of disuldes maybe accomplishedbyallowing the mixture to settle, in which"'case zone 26 will resembleand function similarly to settler 17.

As hereinbefore set vforth,thefpartly treated gasoline withdrawnrfromthe upper portion of extractor 3 through line 6 issubstantiallyjreduczed in mercaptanV content but is not sweet.Sweetening of the gasoline is accomplished in a novel method inaccordance with the present invenftion. In this methodthe gasoline isdirected `by way of line 6 into nal treater 32, preferably through asuitable spray. arrangement as illustrated at 33, and is contactedtherein with a minor portion of the regenerated caustic solution, nowfree from disullides but containing sorbed loxygen and/oroxygencompounds and cobalt phthalocyanine disulfonatecatalyst, suppliedVby way of line 34 to zone 32. In many cases the. regenerated causticsolution contains suicient oxygen and/or oxygen compounds for effectingnal sweetening. In other cases, there may be a deficiency of oxygen and,in suchcase's, all or a portion of the regenerated caustic solution ispas`s`ed from line 34 through line v36 into oxidizer 37,` preferablythrough a suitable sprayarrangement illustrated at 38. Air or othersuitable oxidizing mediumis introducedinto `zone 37 by way of` line 39and spray device 40. In zone 37 the regenerated caustic solution is`countercurrently contacted with an ascending streamiof ,air to therebyincrease the concentration of oxygen or oxygen-containing compounds inthe caustic solution. Excess airis removedfrom zone 37 through line 41.The oxidized caustic solution is Withdrawn from the lower portion ofzone 37 through line 42 and'is directed into line 34 and passed to finaltreater 32.

As hereinbefore set forth, nal sweetening of the gasoline isaccomplished by means of the ,oxygen and/or oxygen compounds containedin the caustic solution. Here again it is only because Yof the veryactive cobalt .phthalo'cyanine disulfonate catalyst that this finalsweetening is accomplished readily jin this manner. Final sweetening isaccomplishedin zone 32 at substantially the same temperature andpressure conditions heretofore described connection .withextractor 3.vSweet gasoline is withdrawn from the upper portion of zone 32 throughline 43 and may be withdrawn from the process through line 44. Thecaustic solution is withdrawn from zone 32 through line 45 andpreferably is returned by way of line 7 to regenerator 9 for furthertreatment and subsequent reuse in the process.

In general it is preferred to effect the final sweetening iu a zoneseparate from extractor 3. However, in another embodiment of theinvention, linal sweetening may be effected in the upper portion ofextractor 3 and in open communication therewith. In this embodiment, theregenerated caustic solution containing oxygen and oxygen-containingcompounds is introduced into extractor 3 atan uppermost point thereof,while the regenerated caustic solution which had been heated and reactedto remove oxygen compounds is introduced at an intermediate point inextractor 3 although, in another embodiment, both of these recycledcaustic solution streams may be commingled and introduced as a singlestream at the upper portion of extractor 3.

When desired,` ,the sweetened gasoline being withdrawn from zone 32 byway of line33 may be subjectedto water wash to` remove any entrainedcaustic solution. This is accomplished by .directing the sweetenedgasoline ,through line 43 and line 46 into wash zone 47, preferablythrough a suitable spray device illustrated at 48. t Infzone 47-thegasoline is passed countercurrently to a descending stream of water,introduced through line 49 into wash zone 47, preferably through asuitable spray device illustrated at 50. Water containing caustic isremoved from the lower portion-of zone 47 through line 51 and may bereusedpdiscarded or used for any suitable purpose, while the sweetenedgasoline is withdrawn fromthe upper portionof zone 47 through line 52.-

As` hereinberore setforth, still further improved r .sults are ,obtainedwhen a solutizer is used. The solutizer serves togincrease solubility ofthe mercaptans in the caustic solution and therebyenhances conversionand extraction of mercaptans. A particularly preferred solutizer ismethanol. However, for an economical commercial process, it isimportant` to prevent loss of methanol from the process.. The drawingillustrates one method Vof recoveringthe methanol which is dissolved inthe sweetened gasoline and/ or entrained in the excess air stream. Inthis embodiment the treated gasoline is directed from zone 32 by way ofline 46 into wash'zone 47, where it is countercurrently contacted withwater in the manner heretofore described.l Similarly,-excess `air fromregenerator 9 is directed by way of lines 12 and 53 into wash zonel 54,preferably througha suitable spray arrangement illustrated atSS.v AWateris introduced into zone 54 by way of line 56 and preferably through asuitable spray arrangement illustrated at 57. In a preferredembodiment,water containing methanol is withdrawn from zone 54 through line 58 andcommingled ,with water withdrawn from zone 47 by way of line v51 and,,while allor a .portion may be removed from'the process by way of line59, at least a portion is directed through line 60 into methanolfractionator 61. Excess `air is withdrawn 4from the upper portionof zone54 through line 77..

In zone 61 the methanol-water stream is subjected to heating anddistillation by any suitable means such as reboiler 62, or in anyV othersuitable manner. In zone 61 methanol is separated from water and thelatter is removed therefrom through line `63. A portion of the water isdirected by way of yline 64 into and through reboiler 62 and returned byway of line 65 into fractionator 61. The water withdrawn through line 63may be removed, in part, from the system through line 66 but preferablyis recycled through line 67 to wash zones 47 and/ or 54. Additionalwater, when required, may be introduced into the system through line 66.Methanol is removed from the upper portion of zone 61 through line 68and directed into and through condenser 69 and line 70 to Y receiver 71,having conventional gas release line 72. Methanol is withdrawn fromreceiver 71 through line 73, a portion being recycle'dby wayvof line 74to the upper portion of zone 61to serve as a cooling and refluxingmedium therein. The remaining portion of the methanol is directed by wayof line 75 and, while all or a portion may be withdrawn from 'theprocess through line 76, preferably at least a portion of the methanolis` directed through lines 75 and 19 and returned by way of line 4 toextractor 3. Line 76 may be utilized for the introduction of theoriginal or additional methanol as desired. When desired, the methanolmay be introduced into extractor 3 at a point beneath the introductionof the caustic solution. This has'the advantage of using the causticsolution to extract methanol which may be entrained in the ascendinggasoline.

In the interest of simplicity, pumps, compressors, valves and otherappurtenances have been omitted from the drawing. It is understood thatthese will be provided as requiredfand also that heat exchangers,heaters, etc. will be provided when elevated temperatu-res are employedin the various steps of the process and also coolers or condensers asmay be required.

From the above descriptions it will be noted that an improved processfor sweetening sour hydrocarbon distillateis provided. As hereinbeforeset forth,` a sweet gasoline is :readily produced without the necessityof resorting to complicated and costly methods of the prior art, such ascopper treating, etc. Also, the process permits regeneration of thealkaline solution by oxidation, which avoids the high temperaturesrequired in the prior art method of high temperature hydrolysis which,in turn, has the disadvantage of adversely aifecting plant equipment andrequiring comparatively frequent replacement thereof. The improvedprocess of the present invention is attainable only because of therecent availability of the phthalocyanine catalyst which is both anactive oxidation catalyst and is stable under the conditions used inVthe process. vWithout such a catalyst, satisfactory regeneration of thecaustic solution is not obtained. Furthermore, the gasoline product doesnot contain metal components resulting from decomposition of thecatalyst during use. As will be shown in the examples appended to thepresent specifications, cobalt phthalocyanine disulfonate has been usedfor an extensive period of time and, to the limit of present analyticalmethods, shows no change in composition or activity. Furthermore, thegasolineproducts are free froml cobalt which further confirms the highstability of the cobalt phthalocyanine disulfonate catalyst. Y

The following examples areintroduced to illustrate further the noveltyand utility of the present invention but not with the intention ofunduly limiting the same.

Example I Y The gasoline used in this example was a' cracked gasolinehaving a -total sulfur content of 0.096% by weight and a mercaptansulfur of 0.045% by'weight. The gasoline was treated with a renerycaustic solution of about 10% by weight concentration. In a continuouslaboratory treatment, 1,000 cc. per hour of gasoline was charged. 90 cc.per hour ofthe 10% by weight caustic solution containing 50 `parts permillionrby weight of cobalt phthalocyanine disulfonate was utilized. Theextraction Was eifected at room temperature. The treated gasolineremoved from the extractor had a mercaptan sul-fur content of 0.003% byweight. The caustic solution containing cobalt phthalocyaninedisulfonate was regenerated at room temperature by contacting 700 cc. ofair per hour.

The regenerated caustic solution contained disuldes dis- F persedthereinand was coalesced at room temperature by being passed through a bed ofDesicote treated sand and' then passed into a settler. A disulde layerwas removedfrom the upper portion of the settler and a regeneratedcaustic solution containing cobalt phthalocyanine disulfonate wasremoved from the lower portion of the settler. A portion by volume) ofthe regenerated caustic solution containing the phthalocyanine catalystwas commingled with a portion (10% by volume) of the rich causticsolution withdrawn from the lower portion of the extractor and themixture was heated to a temperature of 195 F., washed with naphtha toremove disulfides and then recycled for further use in the extractionzone. The remaining portion(20% by volume) of the regenerated causticsolution containing cobalt phthalocyanine was found to contain suicientoxygen and/ or oxygen compounds to effect nal sweetening and,accordingly, was contacted with the partly treated gasoline in a finaltreating zone at Aroom temperature. The gasoline withdrawn from the naltreater was doctor sweet.

Example Il In another run similar to that described in Example I, theregenerated caustic solution withdrawn from the settler, before use inthe iinal treater to effect sweetening Vof the gasoline, iscountercurrently contacted with air. The air is introduced at a rate of4 cc. per hour, and the regenerated caustic solution at a rate of 3.6cc. per hour. This operation is utilized when the regenerated causticsolution does not contain sufficient oxygen or oxygen-containingcompounds to accomplish the nal sweetening of the gasoline.

' Example III In still another run similar to Example I, approximately24% by weight of phenols were added to the caustic solution in order toincrease solubility of the mercaptans in the caustic solution. Thecaustic solution was regenerated by being countercurrently contactedwith air in the presence of the cobalt phthalocyanine catalyst, and thenwas used to further treat lthe partly treated gasoline from theextractor. A doctor sweet product was obtained from the nal treater.

Example IV The cobalt phthalocyanine catalyst was used in the rundescribed in Example I and in many other runs to treat approximately30,000 cc. of gasoline. Additional caustic solution was added in-'thevarious runs as required. Computed on a commercial scale, an equivalentof one pound of cobalt phthalocyanine disulfonate catalyst is used totreat approximately 6,000 barrels of gasoline. As hereinbefore setforth, no change in activity or composition of the cobalt phthalocyaninedisulfonate catalyst was detected and thus it still may be used to treatadditional quantities of gasoline. In all these runs, a sweet gasolinewas obtained from the nal treater.

Example V In this example sour kerosene is treated in a system in whichvanadium phthalocyanine disulfonate is utilized as the catalyst. Thesour kerosene contains 0.01% by weight of mercaptan sulfur and issubjected to countercurrent extraction with 25% potassium hydroxidesolution at ambient temperature.,` The treated kerosene is withdrawnfrom the upper portion of the extractor and now has amercaptan'contentof 0.001% by Weight. The potassium hydroxide solution is regenerated byblowing i with air at ambient temperature in a regeneration zone in theVpresence of the dissolved vanadium phthalocyanine disulfonate catalyst.The regenerated potassium hydroxide solution is coalesced and settled. Aportion by volume) of the regenerated caustic solution is heated to atemperature of 60 C. and passed into a settler, wherefrom a disruldelayer is withdrawn and the regenerated caustic solution, now free'fromsulfides, is recycled through the extraction zone. The remaining portion(15% by volume) of the regeneratedcaustic solution is oxidized by beingpassed countercurrently to an ascending stream of air and thenis`contacted at ambient temperature withY the partly 'treated keroseneVwithdrawn from the upper portion of the extraction zone. A substantiallysweet kerosene is recovered as the product of the inal treater and issubjected to countercurrent washing with water to remove entrainedcaustic solution.

We claim as our invention:

1. A continuous regenerative sweetening process which comprisescontacting sour hydrocarbon distillate with an alkaline solutioncontaining a phthalocyanine catalyst in an extraction zone, separatelywithdrawing therefrom a partly treated hydrocarbon distillate and a usedalkaline solution containing sulfur compounds and said phthalocyaninecatalyst, contacting the last mentioned alkaline solution with anoxygen-containing gas to substantially completely regenerate thealkaline solution and to oxidize the sulfur components to disulfdes in aregeneration zone, said reactions being catalyzed by the phthalocyaninecatalyst, withdrawing therefrom regenerated alkaline solution containingdisullides, phthalocyanine catalyst and entrained oxygen, separatingsaid regenerated solution into a disulde phase and an alkaline solutionphase, reducing the oxygen content of a first portion of the separatedalkaline solution andreturning the same to said extraction zone forfurther use therein to extract mercaptans from sour hydrocarbondistillate, contacting a second portion of the separated alkalinesolution containing phthalocyanine catalyst and entrained oxygen withsaid partly treated hydrocarbon distillate to effect oxidation ofmercaptans remaining in said distillate and to produce a sweethydrocarbon distillate, and separately recovering said sweet hydrocarbondistillate.

2. The process of claim l further characterized in that saidphthalocyanine catalyst s cobalt phthalocyanine disulfonate.

3. The process of claim 1 further characterized in that saidphthalocyanine catalyst is vanadium phthalocyanine disulfonate.

4. The process of claim l further characterized in that said contactingof the sour hydrocarbon distillate with alkaline solution and saidregeneration are eifected at substantially ambient temperature, and saidrst portion of the separated alkaline solution is heated to atemperature ofrfrom about 100 to about 300 F. prior to being returnedto-said extraction zone.

5. The process of claim 4 further characterized in that disuldes areremoved from the heated alkaline solution prior to returning to saidextraction zone.

6. The process of claim 4 further characterized in that a portion of theused alkaline solution withdrawn from said extraction zone and prior toregeneration thereof is comrningled with said second portion of theseparated alkaline solution containing phthalocyanine catalyst and themixture is heated to a temperature of from about 100 4 to about 300 F.,following which disull'ides are removed and the alkaline solution isreturned to said extraction zone for further use therein.

7. The process of claim 1 further characterized in that said secondportion of separated alkaline solution is subjected to oxidation priorto contacting with said partly treated distillate.

8. A continuous regenerative sweetening process which comprisescountercurrently contacting sour gasoline with caustic solutioncontaining a phthalocyanine catalyst in an extraction zone, separatelywithdrawing therefrom a partly treated gasoline and a used causticsolution containing sulfur compounds and said phthalocyanine catalyst,substantially completely regenerating the used caustic solution byoxidizing with air in the presence of the phthalocyanine catalyst and atthe same time oxidizing sulfur compounds to disulfides in a regenerationzone, withdrawing therefrom regenerated caustic solution containingdisultdes, phthalocyanine catalyst and entrained oxygen, separating saidregenerated solution into a disulde phase and a caustic solution phase,reducing the oxygen content of a major portion of the separated causticsolution and returning the same to said extraction zone for further usetherein to extract mercaptans from sour gasoline, contacting a minorportion of said separated caustic solution containing saidphthalocyanine catalyst and entrained oxygen with said partly treatedgasoline to elect oxidation of mercaptans remaining in said gasoline andto produce a sweet gasoline, and separately recovering said sweetgasoline.

9. The process of claim 8 further characterized in that saidphthalocyanine catalyst is cobalt phthalocyanine disulfonate.

10. The process of claim 8 further characterized in that saidphthalocyanine catalyst is vanadium phthalocyanine disulfonate.

l1. The process of claim 8 further characterized in that said reducingthe oxygen content of the major portion of the separated causticsolution is effected by contacting the same with a portion of the richcaustic solution prior to regeneration, whereby the oxygen contained inSaid major portion of caustic solution is consumed by oxidizingmercaptans contained in said rich caustic solution.

12. -The process of claim 8 further characterized in that said reducingthe oxygen content of the major portion of the separated causticsolution is effected by heating the same to a temperature of from aboutto about 300 F., whereby more diicultly reacted mercaptans are oxidizedby the oxygen contained in said major portion of said separated causticsolution.

13. The process of claim 8 further characterized in that said reducingthe oxygen content of said major portion of the separated causticsolution is effected by contacting the same with a portion of the richcaustic solution prior to regeneration and heating the mixture to atemperature of from about 100 to about 300 F., whereby the oxygencontained in said major portion of caustic solution is consumed byoxidizing mercaptans contained in said rich caustic solution and also byoxidation of the more diilicultly reacted mercaptans contained in thecaustic solutions.

14. The process of claim 8 further characterized in that said causticsolution also vcontains methanol and that the sweet gasoline product andexcess air are each separately countercurrently contacted with water torecover methanol carried in said gasoline and air, the water-methanolrecovered therefrom being fractionated to separate methanol from thewater, and each is separately recycled within the process for furtheruse therein.

References Cited in the tile of this patent UNITED STATES PATENTS Gslonet al Nov. 17, 1953

1. A CONTINUOUS REGENERATIVE SWEETENING PROCESS WHICH COMPRISESCONTACTING SOUR HYDROCARBON DISTILLATE WITH AN ALKALINE SOLUTIONCONTAINING A PHTHALOCYANINE CATALYST IN AN EXTRACTION ZONE, SEPARATELYWITHDRAWING THEREFROM A PARTLY TREATED HYDROCARBON DISTILLATE AND A USEDALKALINE SOLUTION CONTAINING SULFUR COMPOUNDS AND SAID PHTHALOCYANINECATALYST, CONTACTING THE LAST MENTIONED ALKALINE SOLUTION WITH ANOXYGEN-CONTAINING GAS TO SUBSTANTIALLY COMPLETELY REGENERATE THEALKALINE SOLUTION AND TO OXIDIZE THE SULFUR COMPONENTS TO DISULFIDES INA REGENERATION ZONE, SAID REACTIONS BEING CATALYZED BY THEPHTHALOCYANINE CATALYST, WITHDRAWING THEREFROM REGENERATED ALKALINESOLUTION CONTAINING DISULFIDES, PHTHALOCYANINE CATALYST AND ENTRAINEDOXYGEN, SEPARATING SAID REGENERATED SOLUTION INTO A DISULFIDE PHASE ANDAN ALKALINE SOLUTION PHASE, REDUCING THE OXYGEN CONTENT OF A FIRSTPORTION OF THE SEPARATED AL-